The present invention relates to an automatic transmission which can realize four forward speeds and one reverse speed by combination of engagement and disengagement of five friction elements through a Ravigneaux planetary gear unit.
There has been proposed an automatic transmission that realizes four forward speeds and one reverse speed by combination of engagement and disengagement of two clutches and three brakes through a Ravigneaux planetary gear unit (a composite planetary gearset composed of two planetary gearsets). Japanese Patent Application Unexamined Publication No. 10-169730 discloses such an automatic transmission in FIG. 9A and FIG. 9B.
However, in the automatic transmission as shown in FIG. 9B of the above conventional art, the following problems are caused due to a layout of the components used.    (1) Deterioration in Noise and Vibration Performance (NV Performance) of an Output Gear:Brake B1 is disposed on an inner circumferential side of the output gear, and the output gear is supported on a transmission case through a hub member of brake B1. Due to the intervention of the hub member of brake B1 between the output gear and the transmission case, a backlash of the output gear is larger than that in a case where the output gear is directly supported by the transmission case. As a result, noise and vibration tend to be generated from the output gear. Further, in the layout in which the hub member of brake B1 is disposed on the inner circumferential side of the output gear, if it is intended to directly support the output gear by the transmission case, an intermediate wall for supporting the output gear must be provided to thereby cause upsizing of the transmission and an increase in cost.    (2) Upsizing of a Control Valve Body and Increase in Cost:
Hydraulic passages on the side of the transmission case and hydraulic passages on the side of the control valve must be connected with each other on one side of the output gear and on the other side of the output gear. For this reason, upsizing of the control valve body is caused, thereby resulting in an increase in cost.    (3) Upsizing of a Common Carrier and Increase in Cost:
A rotary member between a common carrier and clutch C-2 is disposed between two sun gears. Due to this arrangement, a central carrier plate must be additionally provided at a central portion of the common carrier. For this reason, upsizing of the common carrier is caused, thereby resulting in an increase in cost.
The present invention has been made in view of the above problems. It is an object of the present invention to provide an automatic transmission that is capable of enhancing NV performance of an output member and suppressing upsizing of a control valve body and a common carrier to thereby reduce costs thereof.
In a first aspect of the present invention, there is provided an automatic transmission including:                a Ravigneaux planetary gear unit comprising a front sun gear, a rear sun gear, a ring gear, a long pinion meshing with the front sun gear and the rear sun gear, a short pinion meshing with the rear sun gear and the long pinion, and a common carrier on which the long pinion and the short pinion are rotatably supported;        an input member to which rotation of a drive source is inputted;        a first friction element that selectively connects the input member and the front sun gear with each other;        a second friction element that selectively connects the input member and the common carrier with each other;        a third friction element that selectively fixes the rear sun gear to an automatic transmission case;        a fourth friction element that selectively fixes the front sun gear to the automatic transmission case;        a fifth friction element that selectively fixes the common carrier to the automatic transmission case; and        an output member always connected to the ring gear,        the automatic transmission being capable of establishing four forward speeds and one reverse speed by combination of simultaneous engagement of two friction elements selected from the five friction elements,        wherein the output member is disposed on one side of the Ravigneaux planetary gear unit, and        the first friction element, the second friction element, the third friction element, the fourth friction element, and the fifth friction element are disposed on the other side of the Ravigneaux planetary gear unit,        the automatic transmission further including:        a first hub supporting the second friction element on an outer circumferential side thereof, the first hub being connected to a first carrier plate disposed at one end of the common carrier on the one side of the Ravigneaux planetary gear unit,        a second hub supporting the fifth friction element on an outer circumferential side thereof, the second hub being connected to a second carrier plate disposed at the other end of the common carrier on the other side of the Ravigneaux planetary gear unit, and        a partition member cooperating with the automatic transmission case to define a transmission chamber in which the output member, the Ravigneaux planetary gear unit, and the respective first to fifth friction elements are accommodated;        wherein the output member is supported on a cylindrical portion extending from the partition member toward the Ravigneaux planetary gear unit in an axial direction of the input member.        
In a second aspect of the present invention, there is provided the automatic transmission according to the first aspect, wherein the input member is disposed on an inner circumferential side of the Ravigneaux planetary gear unit, and                the first hub extends through an outer circumferential side of the input member, and is connected with the first carrier plate,        the automatic transmission further including:        a first drum supporting the second friction element on an inner circumferential side thereof, the first drum supporting the first friction element on an outer circumferential side thereof such that the first friction element is overlapped with the second friction element in a radial direction of the input member, the first drum being connected to the input member,        a second drum supporting the first friction element on an inner circumferential side thereof, the second drum extending through an outer circumferential side of the first hub and an inner circumferential side of the rear sun gear and being connected to the front sun gear,        a third hub supporting the third friction element on an outer circumferential side thereof, the third hub extending through an outer circumferential side of the second drum and being connected to the rear sun gear, and        a fourth hub supporting the fourth friction element on an outer circumferential side thereof, the fourth hub being connected to the second drum in such a position that a distance of the fourth hub from the Ravigneaux planetary gear unit is larger than a distance of the first friction element from the Ravigneaux planetary gear unit on the other side of the Ravigneaux planetary gear unit,wherein the second hub is disposed on an outer circumferential side of the third hub.        
In a third aspect of the present invention, there is provided the automatic transmission according to the second aspect, wherein the third friction element is arranged on the outer circumferential side of the second friction element such that the third friction element is overlapped with the second friction element in a radial direction of the input member.
In a fourth aspect of the present invention, there is provided the automatic transmission according to the third aspect, wherein the third friction element is arranged on the outer circumferential side of the first friction element such that the third friction element is overlapped with the first friction element in the radial direction of the input member.